Traditionally flexible pipe is utilized to transport production fluids, such as oil and/or gas and/or water, from one location to another. Flexible pipe is particularly useful in connecting a sub-sea location to a sea level location. Flexible pipe is generally formed as an assembly of a flexible pipe body and one or more end fittings. The pipe body is typically formed as a composite of layered materials that form a fluid and pressure-containing conduit. The pipe structure allows large deflections without causing bending stresses that impair the pipe's functionality over its lifetime. The pipe body is generally, but not necessarily, built up as a composite structure including metallic and polymer layers.
Flexible pipe may be utilized as a flowline over land and/or at a sub-sea location. Flexible pipe may also be used as a jumper or riser.
A flexible riser is a flexible pipe used to connect a compliant top side structural system with a sea bed location. A flexible riser system can be designed for many types of floating production structures and some well known riser configurations are free hanging catenary risers, lazy “S” risers, lazy “wave” risers, steep “wave” risers or the like. Such configurations are selectively suitable for use in shallow, medium, deep or ultra deep water depths.
During use it is appreciated that a flexible pipe is subjected to dynamic loading due to a number of possible conditions, for example due to motion of a vessel or platform on a surface of sea. Surge motion and heave motion of such surface bound vessel can particularly cause curvature changes in a riser configuration. Dynamic loading can also occur due to content density changes in the flexible pipe and current/tidal effects. Over bending can also occur when the flexible pipe is installed. It is generally advantageous to prevent shape changes or control such changes within predetermined limits when loading occurs.
One particular problem which is well known where flexible pipe is forced to bend is that the pipe may be damaged if the pipe is bent through too tight a radius. A recognized solution to this problem is the fitting of a bend stiffener at locations where the flexible pipe body is likely to be subjected to over flexing particularly at the interface between the pipe and an end termination or at the interface with a topside structure. The bend stiffener typically comprises a flexible molded polyurethane body having a generally tapered cross section. The thick end of the bend stiffener which is substantially rigid can be secured to fixed points. A degree of bending allowed for the flexible pipe steadily increases towards a tapered narrow end of the bend stiffener. During operation substantial heating can occur at the interface between the stiffener flexible casing and the flexible pipe body. Also the interface between the flexible pipe and bend stiffener tends to be subject to relatively high temperatures due to the lack of a means to limit the temperature (sea water cools a remainder of the flexible pipe) and the high temperatures of the transported production fluids. The heat can cause a deleterious effect to the working lifetime of the flexible pipe and bend stiffener arrangement.
A partial solution to this problem has been suggested in U.S. Pat. No. 6,009,907. Here a stiffener designed for fitting to a flexible conduit for use in a marine environment is disclosed. The stiffener comprises a flexible case located at least partially over the flexible pipe with structures in the bend stiffener being included to form channels which can be used to dissipate heat at the interface between the stiffener and flexible conduit.
However, the solution posed in the '907 patent requires the use of complex parts for a bend stiffener to be manufactured which can increase costs and installation times. Also, the channels in the bend stiffener proposed do not extend along the full length of the bend stiffener covering the flexible pipe. As a result areas under the stiffener are not irrigated and thus cooling water is not circulated across the full region of flexible pipe body surrounded by the bend stiffener. Heat is thus not effectively removed from areas of the interface which can have a negative effect on the lifespan of the pipeline.
It is an aim of embodiments the present technology to at least partly mitigate the above-mentioned problems.
It is an aim of embodiments of the present technology to provide a method for dissipating heat from a region of flexible pipe covered by a bend stiffener.
It is an aim of embodiments of the present technology to dissipate heat from a whole region of flexible pipe surrounded by a bend stiffener.
It is an aim of embodiments of the present technology to provide a method of dissipating heat from a region of flexible pipe body covered by a bend stiffener utilizing a methodology which is relatively cost effective to manufacture and simple to install.
According to a first aspect of the present technology there is provided a method of dissipating heat from a region of flexible pipe covered by a bend stiffener, comprising the steps of:
via at least one channel in an outer surface around a flexible pipe, providing a flow path for water to flow from a region of the flexible pipe covered by a bend stiffener to an uncovered region of the flexible pipe.
According to a second aspect of the present technology there is provided flexible pipe body for transporting production fluids, comprising:
a plurality of coaxially orientated layers; and
at least one channel in an outer surface around the flexible pipe, each channel providing a flow path for water to flow from a region of the flexible pipe body covered by a bend stiffener to an uncovered region.
According to a third aspect of the present technology, a method of transporting a fluid comprises:
providing a flexible pipe comprising a plurality of coaxially orientated layers, at least one channel in an outer surface around the flexible pipe, each channel providing a flow path for water to flow from a region of the flexible pipe body covered by a bend stiffener to an uncovered region, and at least one end fitting; and
transporting fluid through the flexible pipe.
Embodiments of the present technology provide a practical solution for dissipating heat from a region of flexible pipe covered by a bend stiffener. By forming channels in an outer surface of a flexible pipe or in an outer surface of a sleeve slid over the flexible pipe water can be made to flow along channels to constantly remove heat from the annulus region at the interface between the bend stiffener and flexible pipe body or outer sleeve.
The channels may be either machined or molded into the outer surface of the flexible pipe or the outer sleeve in a very convenient process to provide paths by which seawater can circulate and thus moderate the temperature. As a result time consuming and costly manufacture of a bend stiffener is obviated. Also installation times are reduced. Water flows through the channels by natural convection due to thermal gradients and/or the dynamic motion of the flexible pipe and bend stiffener which causes a pumping action. The interface is thus automatically and repeatedly cooled.
The foregoing and other features and advantages of the technology will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.
In the drawings like reference numerals refer to like parts.